Cell Systems: Nuclear Transport and Endomembrane Functions

Nuclear envelope

Double membrane surrounding the nucleus.

Nuclear pore complex

Structure regulating molecule passage in/out of nucleus.

Nuclear localization signal (NLS)

Sequence directing molecules into the nucleus.

Endomembrane system

Network of membranes for manufacturing and shipping.

Pulse-chase experiment

Technique to track molecule fate over time.

Secretory pathway

Pathway for protein transport: ER to Golgi.

ER signal sequence

Amino acid sequence targeting proteins to ER.

Signal Recognition Particle (SRP)

Binds ER signal sequence, halts protein synthesis.

Translocon

Channel for protein entry into the ER.

Glycoprotein

Protein with carbohydrate groups attached.

Exocytosis

Process of vesicle fusion with plasma membrane.

Endocytosis

Process of internalizing substances into the cell.

Receptor-mediated endocytosis

Uses receptors to internalize specific macromolecules.

Phagocytosis

Process of engulfing large particles or cells.

Autophagy

Degradation of damaged organelles via lysosomes.

Middle lamella

Layer connecting adjacent plant cells.

Tight junctions

Cell junctions forming waterproof barriers.

Desmosomes

Structures providing strong cell adhesion.

Cadherins

Proteins facilitating selective cell-cell adhesion.

Gap junctions

Channels connecting animal cells for communication.

Hormones

Molecules signaling between distant cells.

Signal transduction

Conversion of signals into cellular responses.

G proteins

Proteins activated by GTP for signaling.

Second messenger

Nonprotein molecule relaying signals inside cells.

Phosphorylation cascade

Amplification of signals via sequential phosphorylation.

Mitogen-activated protein kinases (MAPKs)

Enzymes activating cell division processes.

Crosstalk

Interactions between signaling pathways modifying responses.